Smoke Detector Requirements - 2000 IMC

[KenRad]

In Chapter 6 (Duct Systems) Section 606 of the 2000 International Mechanical Code, there is an exception that states the following:

"Smoke detectors shall not be required where air distribution systems are incapable of spreading smoke beyond the enclosing walls, floors and ceilings of the room or space in which the smoke is generated."

The way I see this, they are making an exception for single zone systems that cannot develop a positive pressure in the room -- that is, they either do not take in outside air, or they exhaust more than they bring in.

Does anyone have an experience with this exception?

---KenRad

 

[pegboy]

I think you're right about this. I've used this exception for areas like school gyms and theater houses where only one zone is involved. On a packaged rooftop system, I usually provide a powered exhaust fan to placate the code official about pressurizing the space.

Also, you can't use a common return plenum with any other space, either!

 

[CountOlaf]

I think you're correct in that they are referring to single zone systems, however I don't think the negative pressure of the zone is at issue. I've assumed this exception on many computer room or telecom room or electrical equipment room cooling type units where we are simply recirculating the air. There's not necessarily any exhaust or outside air introduction. The key is if there is a fire in the zone in question, the specific air handling unit, even if it continues to operate, won't be able to spread the smoke to other zones not in the immediate fire area.

 

[ChasBean1]

KenRad, this relates specifically to return air ducts (606.2.1) or return air risers (606.2.3). The exception means that if the return airstream in question does not have the potential to take air from the smoke affected room and deliver it to other areas outside the boundaries of that room, the detector may be omitted. As I see it, room pressure or outside air intake are not factors. -CB